Codebook for full-dimension multiple input multiple output communications

ABSTRACT

Various embodiments include an apparatus to be employed by an enhanced Node B (eNB), the apparatus comprising communication circuitry to receive, from a user equipment (UE), feedback information and control circuitry, coupled with the communication circuitry, to identify a codeword from a three-dimensional codebook based on the feedback information received from the UE, wherein the communication circuitry is further to precede data to be transmitted to the UE based on the codeword. An apparatus to be employed by a UE and additional methods are described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/031,438, now U.S. Pat. No. 10,727,914 filed Jul. 10, 2018, andentitled “CODEBOOK FOR FULL-DIMENSION MULTIPLE INPUT MULTIPLE OUTPUTCOMMUNICATIONS”, which is a continuation of U.S. application Ser. No.15/216,378, now U.S. Pat. No. 10,158,406, filed Jul. 21, 2016, andentitled “CODEBOOK FOR FULL-DIMENSION MULTIPLE INPUT MULTIPLE OUTPUTCOMMUNICATIONS,” which is a continuation of U.S. application Ser. No.14/668,655, now U.S. Pat. No. 9,425,875, filed Mar. 25, 2015, andentitled “CODEBOOK FOR FULL-DIMENSION MULTIPLE INPUT MULTIPLE OUTPUTCOMMUNICATIONS,” which claims priority to U.S. Provisional ApplicationNo. 62/055,569, filed Sep. 25, 2014 and entitled “3D CODEBOOK FORFULL-DIMENSION MULTIPLE INPUT MULTIPLE OUTPUT (FD-MIMO) COMMUNICATIONS”,which are hereby incorporated by reference in their entireties.

FIELD

Embodiments of the present disclosure generally relate to the field ofwireless communication, and more particularly, to a codebook forfull-dimension multiple input multiple output (FD-MIMO) communications.

BACKGROUND

Dual-codebook was introduced in Release 10 of the 3rd GenerationPartnership Project (3GPP) Long Term Evolution (LTE) standard forbeamforming of a MIMO antenna array. However, the dual-codebook can beused for the beamforming for at most 8 transmission antennas. Thebeamforming for a MIMO antenna array of more antennas is desired.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates a wireless communication network inaccordance with various embodiments.

FIG. 2 schematically illustrates an eNB in accordance with someembodiments.

FIG. 3 schematically illustrates an antenna structure in accordance withsome embodiments,

FIG. 4 schematically illustrates the antenna structure of FIG. 3 inwhich antenna elements are re-indexed.

FIG. 5 schematically illustrates a UE in accordance with someembodiments.

FIG. 6 is a flowchart describing a method to be performed by an eNB inaccordance with some embodiments,

FIG. 7 is a flowchart describing a method to be performed by a UE inaccordance with some embodiments,

FIG. 8 is a block diagram of an example computing device that may beused to practice various embodiments described herein.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof wherein like numeralsdesignate like parts throughout, and in which is shown by way ofillustration embodiments that may be practiced. It is to be understoodthat other embodiments may be utilized and structural or logical changesmay be made without departing from the scope of the present disclosure,

Various operations may be described as multiple discrete actions oroperations in turn, in a manner that is most helpful in understandingthe claimed subject matter.

However, the order of description should not be construed as to implythat these operations are necessarily order dependent. In particular,these operations may not be performed in the order of presentation,Operations described may be performed in a different order than thedescribed embodiment. Various additional operations may be performedand/or described operations may be omitted in additional embodiments.

For the purposes of the present disclosure, the phrases “A or B” and “Aand/or B” mean (A), (B), or (A and B). For the purposes of the presentdisclosure, the phrase “A, B, and/or C” means (A), (B), (C), (A and B),(A and C), (B and C), or (A, B and C). The description may use thephrases “in an embodiment,” or “in embodiments,” which may each refer toone or more of the same or different embodiments. Furthermore, the terms“comprising,” “including,” “having,” and the like, as used with respectto embodiments of the present disclosure, are synonymous.

As used herein, the term “circuitry” may refer to, be part of, orinclude an Application Specific Integrated Circuit (ASIC), an electroniccircuit, a processor (shared, dedicated, or group) and/or memory(shared, dedicated, or group) that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablehardware components that provide the described functionality.

FIG. 1 schematically illustrates a wireless communication network 100 inaccordance with various embodiments. Wireless communication network 100(hereinafter “network 100”) may be a 3rd Generation Partnership Project(3GPP) long-term evolution (LTE) network (or an LTE-Advanced (LTE-A)network), including an enhanced node base station (eNB) 102 configuredto wirelessly communicate with user equipments (UEs), such as UE 112 andUE 114. The eNB 102 includes an antenna array having a plurality ofantennas, which may transmit signals to the UEs according to a specifiedcodeword in a codebook. For example, the eNB 102 may transmit areference signal from each antenna element of the antenna array to theUE 112, UE 112 then measures the reference signal to obtain the channelstate information (CSI) regarding each channel associated with eachantenna element of the antenna array. The CSI may indicate a codewordthat may achieve a desired transmission throughput. Then, the eNB 102may use the codeword for transmitting signals to the UE 112. Thecodebook includes a plurality of codewords, each of which may be aprecoding matrix.

FIG. 2 schematically illustrates an eNB 200 in accordance with someembodiments. The eNB 200 may be similar to, and substantiallyinterchangeable with, the eNB 102 of FIG. 1 . The eNB 200 may include a3D codebook 202, control circuitry 204, communication circuitry 206 andan antenna array 208. The 3D codebook 202 stores a plurality ofcodewords for the beamforming of the antenna array 208. The controlcircuitry 204 may be coupled with the 3D codebook 202 and thecommunication circuitry 206. For communication with a UE, the eNB 200may transmit a channel state information reference signal (RS),previously known to the UE, by the communication circuitry 206 with theantenna array 208 with no precoding. Then, CSI regarding each channelassociated with each antenna element of the antenna array 208 may bereceived from UE. The received CSI may indicate a precoding matrix thatmay achieve a desired throughput for transmissions from the eNB to theUE. The control circuitry 204 may identify the precoding matrix from thecodebook 202 based on the CSI received from the UE, and control thecommunication circuitry 206 to precode the data to be transmitted withthe antenna array 208 to the UE by using the identified precodingmatrix. The codebook including a plurality of codewords, for example,precoding matrixes, may be maintained in both the eNB and the UE.

Due to the 3D codebook introduced in the present application, thebeamforming of an antenna array having more than 8 antennas may beachieved. In various embodiments, the number of antennas in the antennaarray may be a multiple of 8, such as 16, 32 and 64.

FIG. 3 schematically illustrates an antenna structure that may be usedin the present application in accordance with some embodiments, and FIG.4 schematically illustrates the antenna structure of FIG. 3 in whichantenna elements are re-indexed.

As shown in FIGS. 3 and 4 , the illustrated antenna array has M rows andN columns. Totally 2MN antenna elements are contained in the antennaarray. One possible configuration of M and N is M=8 and N=4. In thisconfiguration the 2D planar antenna array contains 64 antenna elements.Half of the antenna elements have slant angle 45 degree and the otherhalf of antenna elements have slant angle−45 degree. Each column is across-polarized array.

One FD-MIMO system can be described by:y=HPx+nwhere y is N_(r)×1 vector, H is N_(r)×N_(t) matrix, P is N_(t)×N_(p)matrix, x is N_(p)×1 vector, n is N_(r)×1 vector, N_(r) is number ofreceiving antennas, N_(t) is number of transmitting antennas, N_(p) isnumber of layers. If the antenna array is 2D antenna array as shown inFIG. 3 . N_(t)=2NM and N_(t) is usually much larger than 8. For examplewhen N=4 and M=8, N_(t)=64.

In FIG. 4 , the 2D antenna array are re-indexed. The antenna elementshaving −45 degree polarization angle are indexed firstly and then theantenna elements having +45 degree polarization angle are indexed. Then,all antenna elements are indexed row by row.

For an FD-MIMO system, a precoding matrix P is a matrix having Nt rowsand Np columns, wherein Nt is the number of transmitting antennas in theantenna array and Np is the number of layers.

In some embodiments, the codebook includes a plurality of codewords,each of which is constructed as a product of three matrices, forexample, a first matrix, a second matrix, and a third matrix. Each ofthe three matrices may have an index. The product of the second matrixand the third matrix may be the codeword proposed in Release 10 of 3GPPLTE. According to the present application, the codebook dimension may beof 8*N rows and 1 to 8 columns. That is, the precoding matrix may beused for the beamforming of an antenna array having 8*N antennas.

Thus, the first matrix may be an 8*N by 8 matrix. In the first matrix,there may be at most N non-zero elements in each column. The non-zeroelements in all columns of the first matrix may be in different row is.In an embodiment, each of the non-zero elements may be constructed as aDFT vector. In another embodiment, each of the non-zero elements may beconstructed as a non-DFT vector.

In some embodiments, the precoding matrix may depend on a first index ofthe first matrix, a second index of the second matrix, and a third indexof the third matrix. The first index, the second index, and the thirdindex may all be fed back from the UE as the CSI. In variousembodiments, the CSI fed back from the UE may further comprise a rankindicator (RI) and/or a channel quality indicator (CQI).

FIG. 5 schematically illustrates a UE 500 in accordance with someembodiments. The UE 500 may be similar to, and substantiallyinterchangeable with, the UE 112 of FIG. 1. The UE 500 may includecommunication circuitry 502, an antenna 504, computation circuitry 506,feedback circuitry 508, and a 3D codebook 510. The communicationcircuitry 502, the computation circuitry 506 and the feedback circuitry508 may be coupled with each other.

The communication circuitry 502 receives the channel state informationreference signal (RS) from the eNB with the antenna 504. The computationcircuitry 506 determines channel states associated with eachtransmission antenna of the eNB. Based on the determined channel statesassociated with each transmission antenna of the eNB, the computationcircuitry 506 selects a precoding matrix from the 3D codebook 510 fortransmission data from the eNB. The feedback circuitry 508 sendsinformation indicating the selected precoding matrix to the eNB via thecommunication circuitry 502 and the antenna 504.

As described above, each precoding matrix in the codebook may beconstructed as a product of three matrixes, for example, a first matrix,a second matrix, and a third matrix, with each of the matrices having arespective index.

In some embodiments, the computation circuitry 506 may select aprecoding matrix from the 3D codebook 510 so that a desired throughputwill likely be obtained when the selected precoding matrix is used bythe eNB to transmit data to the UE. Various specific measurementcriteria may be used for considering the throughput.

In some embodiments, the codebook dimension is of 2N*M rows and 1 to 2Ncolumns. The precoding matrix may be used for the beamforming of anantenna array having 2N*M antennas. Thus, the first matrix may be a 2N*Mby 2N matrix. In the first matrix, there may be at most N non-zeroelements in each column. The non-zero elements in all columns of thefirst matrix may be in different rows. In an embodiment, each of thenon-zero elements may be constructed as a DFT vector. In anotherembodiment, each of the non-zero elements may be constructed as anon-DFT vector.

In some embodiments, the precoding matrix may depend on a first index ofthe first matrix, a second index of the second matrix, and a third indexof the third matrix. The first index, the second index, and the thirdindex may all be fed back from the UE as the CSI. In variousembodiments, the CSI fed back from the UE may further comprise a RIand/or a CQI.

In some embodiments, the first index of the first matrix may not befrequently changed. Thus, in a periodical CSI report, the index of thefirst matrix may be fed back in a period equal to or being multiple ofthe period in which the RI is fed back.

In some embodiments, the first index of the first matrix may not befrequency-sensitive. Thus, in an aperiodic CSI report, the index of thefirst matrix may be fed back as a wideband parameter.

In some embodiments, the preceding matrix P may be constructed by:P(i0,i1,i2)=W ₀(i0)W ₁(i1)W ₂(i2)wherein W₀(i0), W₁(i1) and W₂(i2) are the above mentioned three matrixeswith indexes i0, i1 and i2, respectively. Matrixes W₁(i1) and W₂(i2) arethe same as those proposed in the Release 10 of the 3GPP LTE for 2N=8and in the Release 12 of 3GPP LTE for 2N=4.

If the full channel matrix can be measured by defining a CSI-RS resourcewith {16, 32, 64} antenna ports, the 3D codebook may be defined with upto rank 8 for {16, 32, 64} antenna ports by extending the existingRel-10 8Tx codebook or Rel-12 4Tx codebook.

In some embodiments, the matrix W₁(i1) may be a block diagonal matrix:

${{W_{1}\left( {i1} \right)} = \begin{bmatrix}{X\left( {i1} \right)} & 0 \\0 & {X\left( {i1} \right)}\end{bmatrix}},$where i1=0,1,2, . . . ,15; and

${X\left( {i1} \right)} = {{\begin{bmatrix}1 & 1 & 1 & 1 \\q_{1}^{2i1} & q_{1}^{{2i1} + 1} & q_{1}^{{2i1} + 2} & q_{1}^{{2i1} + 3} \\q_{1}^{4i1} & q_{1}^{2{({{2i1} + 1})}} & q_{1}^{2{({{2i1} + 2})}} & q_{1}^{2{({{2i1} + 3})}} \\q_{1}^{6i1} & q_{1}^{4{({{2i1} + 1})}} & q_{1}^{4{({{2i1} + 2})}} & q_{1}^{2{({{2i1} + 3})}}\end{bmatrix}{where}q_{1}} = {e^{j2{\pi/32}}.}}$

For rank one precoder, the matrix W₂(i2) may be:

${{W_{2}\left( {i2} \right)} \in \left\{ {{\frac{1}{2}\begin{bmatrix}Y \\Y\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}Y \\{jY}\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}Y \\{- Y}\end{bmatrix}},{\frac{1}{2}\begin{bmatrix}Y \\{- {jY}}\end{bmatrix}}} \right\}},$where Y=e_(i)∈{e₁,e₂,e₃,e₄}.

For rank two precoder, the matrix W₂(i2) may be:

${{W_{2}\left( {i2} \right)} \in \left\{ {{\frac{1}{2\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\Y_{1} & {- Y_{2}}\end{bmatrix}},{\frac{1}{2\sqrt{2}}\begin{bmatrix}Y_{1} & Y_{2} \\{jY}_{1} & {- {jY}_{2}}\end{bmatrix}}} \right\}},$where (Y₁, Y₂)=(e_(i),e_(k))∈{(e₁,e₁), (e₂,e₂), (e₃,e₃), (e₄,e₄),(e₁,e₂), (e₂,e₃), (e₁,e₄), (e₂,e₄))}.

In some embodiments, the first matrix Wo(iO) may be constructed byexpanding discrete Fourier transform (DFT) vector:

${W_{0} = \frac{\left\lbrack {w_{0}\left( {i0} \right)}_{m,n} \right\rbrack}{8}},{0 \leq m \leq {N_{t}.{- 1}}},{0 \leq n \leq 7}$where

${w_{0}\left( {i0} \right)}_{m,n} = \left\{ {\begin{matrix}{\frac{1}{\sqrt{M}}e^{{- i}\frac{2\pi}{\lambda}d_{v}{\lfloor\frac{m}{8}\rfloor}\cos{({\theta({i0})})}}} \\0\end{matrix},} \right.$λ is wavelength, d_(v) is the spacing between two vertical antennaelements, and θ(i0)∈{θ_(start)+θ_(step) i0,0≤i0<2^(L)}, θ_(start),θ_(step), and L represent a start zenith angle, a zenith angle step sizeand a codebook size, respectively, each of which may be configured inradio resource control (RRC) configurations. In one example,θ_(start)=78, θ_(step)=6 and L=3. In another example, θ_(start)=78,θ_(step)=3 and L=4.

In some embodiments, the first matrix W₀(i0) may be constructed bycombining 2^(L-1) codewords using DFT vectors and 2^(L-1) codewordsusing non-DFT vectors as follows:

${w_{0}\left( {i0} \right)}_{m,n} = \left\{ {\begin{matrix}{{\frac{1}{\sqrt{M}}e^{{- i}\frac{2\pi}{\lambda}d_{v}{\lfloor\frac{m}{8}\rfloor}\cos{({\theta({i0})})}}},{{m\% 8}==n},{0 \leq {i0} < 8}} \\{{\frac{1}{\sqrt{M}}e^{- {i({\vartheta({{i0},{\lfloor\frac{m}{8}\rfloor}})})}}},{{m\% 8}==n},{8 \leq {i0} < 16}} \\0\end{matrix},} \right.$where

$\vartheta\left( {{i0},\left\lfloor \frac{m}{8} \right\rfloor} \right)$may be designed as such that more than one major channel direction inthe zenith dimension is covered. Thus the vertical antenna pattern for

$\frac{1}{\sqrt{M}}e^{- {i({\vartheta({{i0},{\lfloor\frac{m}{8}\rfloor}})})}}$may have more than one gain peaks, which may be different from the DFTvector which may have one main peak.

In some embodiments, it is also possible to construct the first matrixW₀(i0) by all codewords using non-DFT vectors.

No matter how the first matrix W₀(i0) is constructed, the first matrixmay be 2N*M by 2N matrix that has at most M non-zero elements in eachcolumn, and the non-zero elements in all columns may be in differentrows.

For the constructed matrixes W₀(i0), W₁(i1) and W₂(i2), a first indexi0, a second index i1, and a third index i3 may be selected by the UEconsidering the channel state estimated from the RS signal received fromthe eNB. The first index i0, the second index i1, and the third index i3may be selected so that a desired, for example, large throughput will beachieved if the eNB transmit data to the UE by the antenna array usingthe corresponding precoding matrix.

FIG. 6 illustrates a method 600 in accordance with some embodiments. Themethod 600 may be performed by an eNB such as eNB 102 or 200. In someembodiments, the eNB may include and/or have access to one or morecomputer-readable media having instructions stored thereon, that, whenexecuted, cause the eNB to perform the method 600. The eNB mayadditionally/alternatively have circuitry configured to perform some orall of the operations described with respect to the method 600.

The method 600 may include, at 602, receiving feedback information froma UE. The received feedback information may be determined by the UE fromchannel state reference signal previously received from the eNB formeasuring the channel state associated with each antenna element in theantenna array.

The method 600 may include, at 604, identifying a codeword from athree-dimensional codebook based on the feedback information receivedfrom the UE. In some embodiments, the codebook may be maintained in boththe eNB and the UE and may include a plurality of codewords, each ofwhich is constructed as a product of a first matrix, a second matrix,and a third matrix. In some embodiments, the information fed back fromthe UE may comprise a first index of the first matrix, a second index ofthe second matrix, a third index of the third matrix, and a rankindicator (RI). In some embodiments, a codebook size, a start zenithangle, and a zenith angle step size of the codebook may be configurableby RRC signaling.

The method 600 may include, at 606, precoding data to be transmitted tothe UE based on the code-word. In some embodiments, the first matrix maybe an 8*N by 8 matrix that has at most N non-zero elements in eachcolumn, and the non-zero elements in all columns may be in differentrows. The second matrix and the third matrix may be the matrixesproposed in the Release 10 of the 3GPP LTE. In various embodiments, eachof the non-zero elements in the first matrix r ray be constructed as aDPT vector, a non-UFT vector, or a combination thereof. In someembodiments, the codebook dimension may be of 8*N rows and 1 to 8columns, wherein 8*N is equal to the number of antennas in the antennaarray.

FIG. 7 illustrates a method 700 in accordance with some embodiments. Themethod 700 may be performed by a UE such as UE 112 or 500. In someembodiments, the UE may include and/or have access to one or morecomputer-readable media having instructions stored thereon, that, whenexecuted, cause the UE to perform the method 700. The UE mayadditionally/alternatively have circuitry configured to perform some orall of the operations described with respect to the method 700.

The method 700 may include, at 702, receiving a channel stateinformation reference signal transmitted from an eNB with atwo-dimensional antenna array. The method 700 may include, at 704,measuring channel state information of the antenna array based on thereceived channel state information reference signal. The method 700 mayinclude, at 706, selecting a codeword from a three-dimensional codebookbased on the measured channel state information. The method 700 mayinclude, at 708, feeding information indicating the selected codewordback to the eNB.

In some embodiments, the codebook may be maintained in both the eNB andthe UE and may include a plurality of codewords, each of which may beconstructed as a product of a first matrix, a second matrix, and a thirdmatrix. In some embodiments, the information fed back from the 11E maycomprise a first index of the first matrix, a second index of the secondmatrix, a third index of the third matrix, and a rank indicator (RI). Insome embodiments, a codebook size, a start zenith angle and a zenithangle step size of the codebook may be configurable by RRC signaling.

In some embodiments, the first matrix may be a 2N*M by 2N matrix thatmay have at most M non-zero elements in each column, and the non-zeroelements in all columns may be in different rows. The second matrix andthe third matrix are the matrixes proposed in the Release 10 of the 3GPPLIE for 8Tx and proposed in the Release 12 of the 3GPP LIE for 4Tx. Invarious embodiments, each of the non-zero elements in the first matrixmay be constructed as a DFT vector, a non-DFT vector, or a combinationthereof. In some embodiments, the codebook dimension is of 2N*M rows and1 to 2N columns, wherein 2N*M is equal to the number of antennas in theantenna array.

In some embodiments, the first index of the first matrix may not befrequently changed. Thus, in a periodical CSI report, the index of thefirst matrix may be fed back in a period equal to or being multiple ofthat of the RI.

In some embodiments, the first index of the first matrix may not befrequency-sensitive. Thus, in an aperiodic CSI report, the index of thefirst matrix may be fed back as a wideband parameter.

An eNB and a UE described herein may be implemented into a system usingany suitable hardware and/or software to configure as desired. FIG. 8illustrates, for one embodiment, an example system 800 which comprisesradio frequency (RF) circuitry 804, baseband circuitry 808, applicationcircuitry 812, a memory 816, a display 820, a camera 824, a sensor 828,and an input/output (I/O) interface 832, coupled with each oilier atleast as shown. The application circuitry 812 may include a circuitrysuch as, but not limited to, one or more single-core or multi-coreprocessors. The processor(s) may include any combination ofgeneral-purpose processors and dedicated processors (e.g., graphicsprocessors, application processors, etc.). The processors may be coupledwith the memory 816 and configured to execute instructions stored in thememory 816 to enable various applications and/or operating systemsrunning on the system 800.

The baseband circuitry 808 may include a circuitry such as, but notlimited to, one or more single-core or multi-core processors. Theprocessor(s) may include a baseband processor. The baseband circuitry808 may handle various radio control functions that enable communicationwith one or more radio networks via the RF circuitry. The radio controlfunctions may include, but are not limited to, signal modulation,encoding, decoding, radio frequency shifting, etc. In some embodiments,the baseband circuitry 808 may provide for communication compatible withone or more radio technologies. For example, in some embodiments, thebaseband circuitry 808 may support communication with an evolveduniversal terrestrial radio access network (EUTRAN) and/or otherwireless metropolitan area networks (WMAN), a wireless local areanetwork (WLAN), a wireless personal area network (WPAN). Embodiments inwhich the baseband circuitry 808 is configured to support radiocommunications of more than one wireless protocol may be referred to asmulti-mode baseband circuitry.

In various embodiments, the baseband circuitry 808 may include circuitryto operate with signals that are not strictly considered as being in abaseband frequency. For example, in some embodiments, the basebandcircuitry 808 may include a circuitry to operate with signals having anintermediate frequency, which is between a baseband frequency and aradio frequency.

The RF circuitry 804 may enable communication with wireless networkusing modulated electromagnetic radiation through a non-solid medium. Invarious embodiments, the RF circuitry 804 may include switches, filters,amplifiers, etc. to facilitate the communication with the wirelessnetwork.

In various embodiments, the RF circuitry 804 may include a circuitry tooperate with signals that are not strictly considered as being in aradio frequency. For example, in some embodiments, the RF circuitry 804may include a circuitry to operate with signals having an intermediatefrequency, which is between a baseband frequency and a radio frequency.In some embodiments, some or all of the constituent components of thebaseband circuitry 808, the application circuitry 812, and/or the memory816 may be implemented together on a system on a chip (SOC).

In an embodiment in which the system 800 represents an access node, forexample, an access node 300, the communication circuitry of the accessnode may be implemented in the RF circuitry 804 and/or the basebandcircuitry 808 and the configuration and the control circuitry may beimplemented in the baseband circuitry 808 and/or the applicationcircuitry 812.

In an embodiment in which the system 800 represents a UE, for example,UE 200, the components of the UE, for example, communication circuitry,channel determination circuitry, and interference estimation circuitry,may be implemented in the RF circuitry 804 and/or the baseband circuitry808.

The memory/storage 816 may be used to load and store data and/orinstructions, for example, for the system 800. The memory/storage 816for one embodiment may include any combination of suitable volatilememory (e.g., a dynamic random access memory (DRAM)) and/or non-volatilememory (e.g., a flash memory).

In various embodiments, the I/O interface 832 may include one or moreuser interfaces designed to enable user interaction with the system 800and/or peripheral component interfaces designed to enable peripheralcomponent interaction with the system 800. User interfaces may include,but are not limited to a physical keyboard or keypad, a touchpad, aspeaker, a microphone, etc. Peripheral component interfaces may include,but are not limited to, a non-volatile memory port, a universal serialbus (USB) port, an audio jack, and a power supply interface.

In various embodiments, the sensor 828 may include one or more sensingdevices to determine environmental conditions and/or locationinformation related to the system 800. In some embodiments, the sensorsmay include, but are not limited to, a gyro sensor, an accelerometer, aproximity sensor, an ambient light sensor, and a positioning unit. Thepositioning unit may also be part of, or interact with, the basebandcircuitry 808 and/or the RF circuitry 804 to communicate with componentsof a positioning network, e.g., a global positioning system (GPS)satellite.

In various embodiments, the display 820 may include a display a liquidcrystal display, a touch screen display, etc.

In various embodiments, the system 800 may be a mobile computing devicesuch as, but not limited to, a laptop computing device, a tabletcomputing device, a netbook, an ultrabook, a smartphone, etc. In variousembodiments, the system 800 may have more or less components, and/ordifferent architectures.

The following paragraphs describe examples of various embodiments.

Example 1 includes an apparatus to be employed by an enhanced Node B(eNB), the apparatus comprising: communication circuitry to receive,from a user equipment (UE), feedback information; and control circuitry,coupled with the communication module, to identify a codeword from athree-dimensional codebook based on the feedback information receivedfrom the UE, wherein the communication circuitry is further to precededata to be transmitted to the UE based on the codeword.

Example 2 includes an apparatus of example 1, wherein the communicationcircuitry is to transmit a channel state information signal to the UEusing a two-dimensional antenna array.

Example 3 includes an apparatus of example 1 or 2, wherein thethree-dimensional codebook includes a plurality of codewords, each ofwhich is constructed as a product of a first matrix, a second matrix,and a third matrix.

Example 4 includes an apparatus of example 3, wherein the first matrixis a 2N*M by 2N matrix that has at most M non-zero elements in eachcolumn, and the non-zero elements in all columns are in different rows.

Example 5 includes an apparatus of example 4, wherein each of thenon-zero elements is constructed as a discrete Fourier transform (DFT)vector or non-DFT vector.

Example 6 includes an apparatus of any of examples 3-5, wherein thefeedback information received from the UE comprises a first index of thefirst matrix, a second index of the second matrix, a third index of thethird matrix, and a rank indicator (RI).

Example 7 includes an apparatus of example 6, wherein the first index ofthe first matrix is to be fed back, in a periodical CSI report, in aperiod equal to or a multiple of a period in which the RI is fed back.

Example 8 includes an apparatus of example 6, wherein the first index ofthe first matrix is fed back as a wideband parameter.

Example 9 includes an apparatus of any of examples 1-8, wherein thethree-dimensional codebook comprises 2N*M rows and 1 to 2N columns,where 2N*M is equal to the number of antennas in an antenna array.

Example 10 includes an apparatus of any of examples 1-9, wherein thecontrol circuitry is to configure a codebook size, a start zenith angle,and a zenith angle step size of the three-dimensional codebook by radioresource control (RRC) signaling.

Example 11 includes an apparatus to be employed by a user equipment(UE), the apparatus comprising: communication circuitry to receive achannel state information reference signal transmitted from an enhancedNode B (eNB); computation circuitry, coupled with the communicationcircuitry, to measure channel state information based on the channelstate information reference signal, and select a codeword front athree-dimensional codebook based on the measured channel stateinformation; and feedback circuitry, coupled to the computationcircuitry, to feed back information to indicate the selected codeword tothe eNB.

Example 12 includes an apparatus of example 11, wherein thethree-dimensional codebook includes a plurality of codewords, each ofwhich is constructed as a product of a first matrix, a second matrix anda third matrix.

Example 13 includes an apparatus of example 12, wherein the first matrixis a. 2N*M by 2N matrix that has at most M non-zero elements in eachcolumn, and the non-zero elements in all columns are in different rows.

Example 14 includes an apparatus of example 13, wherein each of thenon-zero elements is constructed as a discrete Fourier transform (DFT)vector or non-DFT vector.

Example 15 includes an apparatus of any of examples 12-14, wherein theinformation fed back to the eNB comprises a first index of the firstmatrix, a second index of the second matrix, a third index of the thirdmatrix and a rank indicator (RI).

Example 16 includes an apparatus of example 15, wherein the first indexof the first matrix is to be fed back, in a periodical CSI report, in aperiod equal to or a multiple of a period in which the RI is fed back.

Example 17 includes an apparatus of example 15, wherein the first indexof the first matrix is fed back as a wideband parameter.

Example 18 includes an apparatus of any of examples 11-17, wherein thethree-dimensional codebook comprises 2N*M rows and 1 to 2N columns, 2N*Mis equal to the number of antennas in the antenna array.

Example 19 includes one or more non-transitory computer-readable mediahaving instructions that, when executed, cause an enhanced Node B (eNB)to: receive feedback information from a user equipment (UE); identify acodeword from a three-dimensional codebook based on the receivedfeedback information; precode data to be transmitted to the UE based onthe identified codeword; and transmit the precoded data to the UE.

Example 20 includes one or more non-transitory computer-readable mediaof example 19, wherein the three-dimensional codebook includes aplurality of codewords, each of which is constructed as a product of afirst matrix, a second matrix and a third matrix.

Example 21 includes one or more non-transitory computer-readable mediaof example 20, wherein the first matrix is a 2N*M by 2N matrix that hasat most M non-zero elements in each column, and the non-zero elements inall columns are in different rows.

Example 22 includes one or more non-transitory computer-readable mediaof example 21, wherein each of the non-zero elements is constructed as aDFT vector or non-DFT vector.

Example 23 includes one or more non-transitory computer-readable mediaof any of examples 20-22, wherein the feedback information received fromthe UE comprises a first index of the first matrix, a second index ofthe second matrix, a third index of the third matrix, and a rankindicator (RI).

Example 24 includes one or more non-transitory computer-readable mediaof example 23, wherein the first index of the first matrix is to be fedback, in a periodical CSI report, in a period equal to or a multiple ofa period in which the RI is fed back.

Example 25 includes one or more non-transitory computer-readable mediaof example 23, wherein the first index of the first matrix is fed backas a wideband parameter.

Example 26 includes one or more non-transitory computer-readable mediahaving instructions that, when executed, cause a user equipment (UE) toreceive channel state information reference signal transmitted from anenhanced Node B (eNB) with a two-dimensional antenna array; measurechannel state information of the antenna array based on the receivedchannel state information reference signal; select a codeword from athree-dimensional codebook based on the measured channel stateinformation; and feed information indicating the selected codeword backto the eNB.

Example 27 includes one or more non-transitory computer-readable mediaof example 26, wherein the codebook includes a plurality of codewords,each of which is constructed as a product of a first matrix, a secondmatrix and a third matrix.

Example 28 includes one or more non-transitory computer-readable mediaof example 27, wherein the first matrix is a 2N*M by 2.N matrix whichhas at most 2M non-zero elements in each column, and the non-zeroelements in all columns are in different rows.

Example 29 includes one or more non-transitory computer-readable mediaof example 28, wherein each of the non-zero elements is constructed as aDFT vector or non-DFT vector.

Example 30 includes one or more non-transitory computer-readable mediaof any of examples 27-29, wherein the feedback information received fromthe comprises a first index of the first matrix, a second index of thesecond matrix, a third index of the third matrix, and a rank indicator(RI).

Example 31 includes one or more non-transitory computer-readable mediaof example 30, wherein the first index of the first matrix is to be fedback, in a periodical CSI report, in a period equal to or a multiple ofa period in which the RI is fed back.

Example 32 includes one or more non-transitory computer-readable mediaof example 30, wherein the first index of the first matrix is fed backas a wideband parameter.

Example 33 includes one or more non-transitory computer-readable mediaof any of examples 26-32, wherein the three-dimensional codebookcomprises 2N*M rows and 1 to 2N columns, 2N*M is equal to the number ofantennas in the antenna array.

Example 34 includes a method comprising: receiving, by an enhanced NodeB (eNB), feedback information from a user equipment (UE); identifying,by the eNB, a codeword from a three-dimensional codebook based on thefeedback information received from the UE; and precoding, by the eNB,data to be transmitted to the UE based on the codeword.

Example 35 includes a method of example 34, wherein thethree-dimensional codebook includes a plurality of codewords, each ofwhich is constructed as a product of a first matrix, a second matrix anda third matrix.

Example 36 includes a method of example 35, wherein the first matrix isa 2N*M by 2N matrix which has at most M non-zero elements in eachcolumn, and the non-zero elements in all columns are in different rows.

Example 37 includes a method of example 36, wherein each of the non-zeroelements is constructed as a DFT vector or non-DFT vector.

Example 38 includes a method of any of examples 35-37, wherein thefeedback information received from the UE comprises a first index of thefirst matrix, a second index of the second matrix, a third index of thethird matrix, and a rank indicator (RI).

Example 39 includes a method of any of examples 34-38, wherein thethree-dimensional codebook comprises 2N*M rows and 1 to 2N columns, and2N*M is equal to the number of antennas in the antenna array.

Example 40 includes a method of any of examples 34-39, which furthercomprises configuring, by the eNB, a codebook size, a start zenith angleand a zenith angle step size of the codebook by RRC signaling.

Example 41 includes a method comprising: receiving, by a user equipment(UE), a channel state information reference signal transmitted from anenhanced Node B (eNB) with a two-dimensional antenna array; measuring,by the UE, channel state information of the antenna array based on thereceived channel state information reference signal; selecting, by theUE, a codeword from a three-dimensional codebook based on the measuredchannel state information; and feeding, by the UE, informationindicating the selected codeword back to the eNB.

Example 42 includes a method of example 41, wherein the codebookincludes a plurality of codewords, each of which is constructed as aproduct of a first matrix, a second matrix and a third matrix.

Example 43 includes a method of example 42, wherein the first matrix isa 2N*M by 2N matrix which has at most M non-zero elements in eachcolumn, and the non-zero elements in all columns are in different rows.

Example 44 includes a method of example 43, wherein each of the non-zeroelements is constructed as a DFT vector or non-DFT vector.

Example 45 includes a method of example 41, wherein the feedbackinformation received from the UE comprises a first index of the firstmatrix, a second index of the second matrix, a third index of the thirdmatrix, and a rank indicator (RI).

Example 46 includes a method of example 45, wherein the first index ofthe first matrix is to be fed back, in a periodical CSI report, in aperiod equal to or a multiple of a period in which the RI is fed back.

Example 47 includes a method of example 45, wherein the first index ofthe first matrix is fed back as a wideband parameter.

Example 48 includes an apparatus having means for performing the methodsof any of claims 34-48.

The description herein of illustrated implementations, including what isdescribed in the Abstract, is not intended to be exhaustive or to limitthe present disclosure to the precise forms disclosed. While specificimplementations and examples are described herein for illustrativepurposes, various equivalent modifications are possible within the scopeof the disclosure, as those skilled in the relevant art will recognize.These modifications may be made to the disclosure in light of the abovedetailed description.

What is claimed is:
 1. One or more non-transitory, computer-readablemedia storing instructions that, when executed by one or moreprocessors, cause a user equipment (UE) in a communications network toperform operations comprising: receiving, from a base station associatedwith the communications network, a channel state information referencesignal (CSI-RS) corresponding to a plurality of channels associated withan antenna array of the base station; measuring, based on the CSI-RS,channel state information (CSI) corresponding to the plurality ofchannels associated with the antenna array of the base station;selecting, based on measuring the CSI, a precoding matrix from amulti-dimensional codebook that includes a plurality of codewordsindicated by a corresponding plurality of precoding matrices, theprecoding matrix selected for transmission from the base station to theUE using antenna elements of the antenna array of the base station,wherein a codeword of the plurality of codewords in the codebook isbased on a plurality of matrices that includes a first matrix, a secondmatrix and a third matrix, wherein the precoding matrix comprises afirst element determined using a first index applied to the firstmatrix, a second element determined using a second index applied to thesecond matrix, and a third element determined using the third matrix,wherein each of the first element, second element and third element is amatrix; generating a feedback report for the base station, the feedbackreport including information about the selected precoding matrix andfurther includes at least one of a rank indicator (RI) or a channelquality indicator (CQI); and transmitting the feedback report to thebase station.
 2. The one or more non-transitory, computer-readable mediaof claim 1, wherein the codebook is a three-dimensional codebook.
 3. Theone or more non-transitory, computer-readable media of claim 1, whereinthe information about the selected precoding matrix in the feedbackreport includes information about the first index applied to the firstmatrix and the second index applied to the second matrix.
 4. The one ormore non-transitory, computer-readable media of claim 1, wherein thefeedback report includes one of a periodic CSI report or an aperiodicCSI report.
 5. The one or more non-transitory, computer-readable mediaof claim 1, wherein the antenna array of the base station includes aplurality of antenna elements, and wherein the selected precoding matrixis used to perform beamforming using the plurality of antenna elements.6. The one or more non-transitory, computer-readable media of claim 1,wherein the selected precoding matrix corresponds to a target throughputof transmission from the base station to the UE.
 7. A processor for auser equipment (UE) in a communications network, the processorcomprising circuitry to perform operations comprising: receiving, from abase station associated with the communications network, a plurality ofchannel state information reference signals (CSI-RS) corresponding to aplurality of channels associated with an antenna array of the basestation; measuring, based on the CSI-RS, channel state information (CSI)corresponding to the plurality of channels associated with the antennaarray of the base station; selecting, based on measuring the CSI, aprecoding matrix from a multi-dimensional codebook that includes aplurality of codewords indicated by a corresponding plurality ofprecoding matrices, the precoding matrix selected for transmission fromthe base station to the UE using antenna elements of the antenna arrayof the base station, wherein a codeword of the plurality of codewords inthe codebook is based on a plurality of matrices that includes a firstmatrix, a second matrix and a third matrix, wherein the precoding matrixcomprises a first element determined using a first index applied to thefirst matrix, a second element determined using a second index appliedto the second matrix, and a third element determined using the thirdmatrix, and wherein each of the first element, second element and thirdelement is a matrix; generating a feedback report for the base station,the feedback report including information about the selected precodingmatrix and further includes at least one of a rank indicator (RI) or achannel quality indicator (CQI); and transmitting the feedback report tothe base station.
 8. The processor of claim 7, wherein the informationabout the selected precoding matrix in the feedback report includesinformation about the first index applied to the first matrix and thesecond index applied to the second matrix.
 9. The processor of claim 7,wherein the feedback report includes one of a periodic CSI report or anaperiodic CSI report.
 10. The processor of claim 7, wherein the antennaarray of the base station includes a plurality of antenna elements, andwherein the selected precoding matrix is used to perform beamformingusing the plurality of antenna elements.
 11. The processor of claim 7,wherein the selected precoding matrix corresponds to a target throughputof transmission from the base station to the UE.
 12. A method performedby a base station in a communications network, the method comprising:sending, to a user equipment (UE) in the communications network, aplurality of channel state information reference signals (CSI-RS)corresponding to a plurality of channels associated with an antennaarray of the base station; receiving, from the UE, a feedback report,the feedback report including information about a precoding matrixselected by the UE from a multi-dimensional codebook that includes aplurality of codewords indicated by a corresponding plurality ofprecoding matrices, the precoding matrix selected for transmission fromthe base station to the UE using antenna elements of the antenna arrayof the base station, wherein a codeword of the plurality of codewords inthe codebook is based on a plurality of matrices that includes a firstmatrix, a second matrix and a third matrix, wherein the precoding matrixcomprises a first element determined using a first index applied to thefirst matrix, a second element determined using a second index appliedto the second matrix, and a third element determined using the thirdmatrix, and wherein each of the first element, second element and thirdelement is a matrix, wherein the precoding matrix is selected by the UEupon measuring, based on the CSI-RS, channel state information (CSI)corresponding to the plurality of channels associated with the antennaarray of the base station, and wherein the feedback report furtherincludes at least one of a rank indicator (RI) or a channel qualityindicator (CQI); determining, based on the information about theprecoding matrix included in the feedback report, a codeword from thecodebook corresponding to the precoding matrix; precoding data fortransmission to the UE based on the determined codeword; andtransmitting the precoded data to the UE using the antenna elements ofthe antenna array.
 13. The method of claim 12, wherein the informationabout the selected precoding matrix in the feedback report includesinformation about the first index applied to the first matrix and thesecond index applied to the second matrix.
 14. The method of claim 12,wherein the feedback report includes one of a periodic CSI report or anaperiodic CSI report.
 15. The method of claim 12, wherein the selectedprecoding matrix corresponds to a target throughput of transmission fromthe base station to the UE.
 16. The method of claim 12, wherein thetransmitting further comprises: performing beamforming using the antennaelements of the antenna array, wherein the beamforming is based at leaston the selected precoding matrix.